Lenovo ThinkPad T460 Yoga with Intel AC 8260 Wireless Issues

I recently came across an issue where the Lenovo ThinkPad T460 Yoga with Intel AC 8260 wireless adapter was having all sorts of issues connecting to and passing traffic across a Cisco 5508 Wireless LAN Controller with 1262N and 3702E Access Points running 8.0.133.0 software, the most recent release at the time of the issue. The first thing we tried was upgrading the driver for the Intel Dual Band Wireless-AC 8260 to 19.1.0.4 (7/16/2016) which was the latest available at the time. Unfortunately that didn’t help any, we also tried applying an 8.0.135.5 software version to the Cisco WLC, again that didn’t help any.

The laptop would often connect to the SSID but the laptop would be unable to get a webpage to render with all IP traffic essentially stalling. ICMP ping times would jump from 1 ms to 3,900 ms with multiple dropped packets scattered all about the constant ping. Without any load you could occasionally get 1 ms response times for a couple of minutes at a time but the instant you opened a web page the traffic would stall and the ICMP pings would start timing out.

The Intel engineer that was assisting me provided the hint, letting me know that Cisco IT had actually stumbled across this very same issue the week earlier internally with their own employees. Cisco had intentionally disabled A-MPDU on their WLCs, the workaround was to enable A-MPDU for 802.11n on their WLCs. I went ahead and checked our WLCs and sure enough we also had A-MPDU disabled – not exactly sure who or why it was disabled.

I’m not 100% sure but I believe we tested v18.30 and found the same issues, actually I believe the factory imaged we had shipped with 18.30… will need to look at my notes.

I haven’t heard of any negative feedback yet but it can sometimes take time to work it’s way back to me if the problem only impacts a small number of clients…. I have about 4,000 clients connecting on a daily basis we usually hear pretty quickly if there is a large scale issue. At this point I’d say that we haven’t run into any issues enabling A-MPDU.

We’ve reproduced the problem in our lab. Interesting note – the problem only occurs on Cisco FW 8.0.X and below. It does not occur with version 8.3.X. This is due to Cisco changing the maximum A-MSDU size. We tested 8.3.X and found that the AP would not send a A-MSDU frame larger than 4 kB. We then tested 8.0.X and found the AP would send a 7.5 kB frame. We know our adapter chokes on frames larger than 4 kB. I’m not sure why Cisco made a change on their side.

This article helped me to solve issues with Thinkpad P50 with AC8260 and Cisco 1262 autonomous accesspoint. It would be nice, if Intel would bother to fix their drivers. Disabling HT or VHT mode on Intel driver limits performance seriously (max 54mbps) and what’s the point of having n- or ac-adapter, if you can only use 802.11g-class transfer rate?!

My solution was also to issue ampdu-command for access point. For autonomous accespoints, command is given on radio interface: interface dot11radio n (n being number of radio) ampdu transmit priority 0 (0, zero being best effort, there are other classes)

Did some tinkering, downgraded my (independent) Cisco AP 1262 from IOS 15.2.4.something to 12.4.25d.JA2 (last version of 12-series IOS). No more problems. Still using Intel 18.40.0.12 driver, because newer didn’t work at all with IOS 15. Tried my P50 at my parents place, they have Cisco AP 1252 with IOS 12.4., no problems. Now having solid connection and no delays.

Have to try newer drivers with 12-series IOS. I ordered Ubiquiti WLAN AP (ac), it will arrive soon, will be interesting to try. So far I have read that certain versions of Ubiquitis firmware work, most doesn’t work. I’ll report results here.

Some more testing done with AC 8260 in Lenovo P50 and different APs. AC 8260 with newest driver (19.20.3.4) in use: – works with Ubiquiti AP AC PRO, didn’t check AP firmware version, default settings on radio interface, just addes two SSIDs. Lot of variation on connection speeds. – works reasonably with Cisco SRP-527 at n-speeds (latest firmware 1.01.29 from year 2013, EOL, non-IOS AP) – works better with Cisco 1262 (12-series IOS) when CCX-extensions are enabled on Intel-driver. Using AMPDU + lower Fragmentation threshold (1024). Somewhat low connection speeds, less than 150Mbps, no matter whether 2.4Ghz or 5GHz band.

In order to enable CCX-extensions on Intel driver one must download ITC / Pro-version that enables customizations. CCX is enabled by altering setup.xml with editor and then running setup. For some reason CCX is disabled by default.

Still not as as reliable as old Centrino Advanced-N 6205 in my old W530. 6205 used to have predictable speeds with precisely same environment and same APs in use, except Ubiquiti that I didn’t have before.

I am also now facing with the same issue. Intel® Dual Band Wireless-AC 8260. My laptop Lenovo ThinkPad Yoga 460. Random ping lost. Testes with several wireless access point (cisco, dlink, zyxel, ubiquiti, hp aruba) A few days ago Intel released 19.40.0 (Latest) version driver. Windows 10 automatically download and install latest version and laptop cant detect wireless signals. I last we discover that wireless adapter can detect signals in short distance, we made hotspot and connect. We also tried to change several parameters of wireless adapter (channel width, HT mode, wireless mode and all other) We rollback to 18.40.0.12 version. Still not effective.

We have similar issues with Lenovo X1 Yoga Gen1/2 running intel 8260/65 chipsets. We upgraded the driver version to latest Version: 20.10.2 but problems continue. Client drops wireless connection, sometimes SSIDs do not show up. Clients connect but show no internet connectivity.

Cisco 5508, AP 2800s Currently running 8.2.166.0

MPDU is enabled in our case. Would it be good to upgrade 8.3.x version. Have a TAC case open for this.